When the printed circuit board was first developed, it was hailed as a major advance in electronics technology over production hard wired boards. The printed circuit board permitted more components to be mounted in a smaller area than previously possible and has rendered the hard wired board obsolete. As the technology evolved, the distance between circuit lines has shrunk and multi-layered boards have been developed.
The density and complexity of printed circuit boards can no longer be matched by hard wired boards. Therefore, even in prototyping a new electronic board, it is often necessary to use substantially the same steps and procedures as would be used for a production printed circuit board.
While there are a number of minor variations, there are generally four steps in producing a printed circuit board. First, the printed circuit board is laid out using a computer aided design (CAD) system. Second, the output of the CAD system is used to provide a pattern image which is a negative of the desired circuit pattern. Third, this negative is then used in a photochemical fabrication process which involves a large number of chemical steps (sometimes as many as fifty-five) to produce the finished circuit pattern. Fourth, a mechanical fabrication process is required to provide through-holes for later connection of components or circuits an opposite sides of the board, and for trimming the board to its final configuration.
In complex, multi-layered boards, an additional mechanical fabrication process is added during mechanical fabrication to bond a number of boards together under high pressure.
Unfortunately, it generally takes weeks and even months to develop a prototype board and place it into production. The state of the art is such that a prototype board may be completed in five to seven days on an expedited basis using totally automated equipment.
Projections have been made that with the most sophisticated automation technology available, the most optimistic idea-to-product time may be three days.
As would be evident, because of the complexity of the boards, there is a vital need to be able to obtain prototype boards as quickly as possible to detect problems and errors and to test out the corrections.
Another problem is that customers are demanding smaller and more individualized electronic products. This means more and more customized boards are required for production runs which are getting shorter. Unfortunately, with customization, the economies of volume production are lost and the end products tend to become relatively expensive.
Thus, the ideal method of manufacturing printed circuit boards should be as rapid as possible while being economical on a small production line basis. Further, the end product would ideally be interchangeable with mass-produced printed circuit boards in order to assure a high degree of confidence that the prototype board will correctly emulate the production boards.